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sketch at C. (See Fig. 4.) They are more frequently set bevelling, so that either the front line of the flat, as at A, or the back line, as at B, almost touches the cylinder. Foster Wilson, a veteran carder, formerly of Lowell, but now of Hol
yoke, Mass., recommends, in his "Carder's Companion," that the front of the flat be set twice as far from the cylinder as the back is, as at B.1
Now, no matter which of these methods of setting the flats
1 That edge of the toothed surface of the flat which the cotton meets first, is, in Mr. Wilson's work, called "the front." I have used the term in the same sense here.
is adopted, as the cotton fibre is, by the action of the cylinderteeth, made to slide from flat to flat, it passes a succession of strictures, or "bights," with enlargements between. At each bight the movement of the cotton is checked, by the teeth of the flat, until it is teazed onward, fibre by fibre.
In flat carding, then, the cotton does not undergo a single process as it passes from the "feed-rolls" or the "licker-in" to the doffer, but each time it passes between the cylinder and a flat there is a repetition of the disentangling, straightening, parallel-laying process at the bight. The fibres enter each succeeding bight, more free from dirt and nep, and more thoroughly disentangled than before.
It has been supposed that to increase the number of these repetitions would be to increase the efficiency of the performance of the card. How many practical men have acted as if this supposition was correct, will appear from a consideration of the fact that there has been a gradual but steady increase in the number of these repetitions. Let us see if it is a fact that there has been such an increase.
About fifty years ago, as I am informed by Mr. Boyden of the Prescott Mills, in Lowell, the flat cards that were in use in Killingly, Conn., had but ten flats each. In 1839 Mr. William A. Burke started the Amoskeag Machine Shop at Manchester, and about 1841 he built some cards. The width of the toothed surface of the older flats was one and five-eighths inches, and the entire width of a flat was about two and a half inches, while the length of staple of the cotton most commonly used was much less. He decided that the process at the bight would be quite as well performed if the distance between two bights was reduced to correspond more nearly with the length of the staple; and he reduced the width of the flats to two inches, and the width of the toothed surface of the flat to an inch and a quarter. This change enabled him to increase the number of flats covering the same space in the proportion of two and a half to two, and to materially increase the efficiency of the card. The new cards had iron frames, and were otherwise improved.
In April, 1845, Mr. Burke took charge of the newly-incorporated Lowell Machine Shop, formerly owned by the Proprietors of the Locks and Canals. He soon brought out the iron frame card with fourteen flats covering .27 of the circumference. (See Fig. 5.)
Both this card, and its predecessor with twelve flats, delivered the sliver into tall cans placed beneath the doffer. (See Figs. 3 and 5.) The first railway-boxes that were built were lined within with smooth tin, had no belts, and were placed high up under the doffer. When the railway-boxes were placed near the floor, they occupied so much less height than the cans had done, that it became possible to drop the doffer down also. Space was thus afforded for the placing of more flats between
those formerly used and the new position of the doffer. at what date this change was made I do not know; but the card, which was being built at Lowell in 1862, had a lowered doffer, with twenty flats, covering .35 of the circumference. (See Fig. 6.)
Several attempts have been made to increase the number of flats by increasing the diameter of the cylinder; but for various reasons these larger cylinders have not been favorably received, and have generally gone out of use.
The feed-rolls, flats, and doffer, in the Lowell card of 1862, occupied about one-half of the circumference. The other half
was not utilized to any important extent.
Built in 1862 at Lowell. 20 Top-flats occupy .35 of the circumference.
In 1874 or 1875, my old shopmate, Mr. Foss, to whom I was indebted for many valuable hints during my apprenticeship at the Lowell Machine Shop, conceived the idea of extending the
flats over a portion of this hitherto unproductive area. He carried the feed-rolls down under the card, and located them on the other side beneath the doffer. (See Fig. 7.) He reasoned that in making this change, he would not only increase the number of repetitions at the bights, but also utilize that portion of the
Built in 1880. 17 Top-flats and 17 Under-flats occupy .76 of the circumference. Lowell Machine Shop.
cylinder which was most valuable for the removal of heavy dirt; for, with under-flats, gravitation would aid centrifugal force in driving the dirt out between the flats, while with top-flats gravitation opposes the centrifugal force. Practical trial has shown that this reasoning was correct.